In recent years, a resistance varying type memory (ReRAM: Resistive RAM) has been drawing attention as a technology for achieving an even higher degree of integration of a semiconductor memory device.
One kind of resistance varying type memory employs an ion conduction memory as a memory cell, the ion conduction memory being configured having a metal layer and an ion conduction layer stacked therein. When this ion conduction memory is applied with an electrical signal, metal atoms included in the metal layer are ionized and migrate within the ion conduction layer to forma filament configured by metal atoms. The ion conduction memory stores different data according to a state of this formed filament.
However, a problem arises that if this ion conduction memory is left in a room or the like, the formed filament gradually changes, whereby a change occurs also in stored data.